Hi,
IRCC require that you write (by correspondence) next to the institution name so that they know that you were not physically present in that country.
http://www.cic.gc.ca/english/resources/tools/perm/express/intake-complete.asp
The people who are rejected for the reason you have mentioned above will not have followed this instruction. Therefore, the office assumes they were there.
So where it say:
Country/territory of study, you enter the country of the University.
Where did this activity take place, you enter the country where you were physically in.
(paraphrasing as I do not remember the exact words they use)
There are no additional document you can send, but you can mention this in your letter of explanation. However, if you follow the instruction, I am confident you wont go wrong.
All the best.